Hollow structural components are frequently used in designs of many types. This type of construction makes it possible to keep the weight of the construction low as well as the cost of materials, but stability and strength are often lost with this type of construction. Because of the larger surface area of the hollow component, these cavities also present a larger surface for attack by corrosion, if moisture or dirt penetrates into them. Likewise, noise caused by wind or vibrations can be transmitted in or along the cavities.
Because of the shape and/or narrow extent of such cavities, it is often difficult to efficiently reinforce and seal them or to prevent noise transmission.
To improve the mechanical properties of structural components containing cavities, for example, it is customary in many cases to use or incorporate local reinforcing elements into the components. Such reinforcing elements can be made of metals or plastics or of combinations of these materials. Structural foams are often used in locations to which access is difficult and which are to be reinforced or sealed only after assembly of the component. This is the case, for example, in the production of automotive structures and/or bodies. The advantage of structural foams is that they can be introduced into a cavity in an unexpanded state and can then be foamed in place, for example, with an increase in temperature. Thus, for example, after assembling the reinforcing element, the inside walls of the cavity may also be coated completely by means of cathodic dip painting (CDP) and only then reinforced by foaming the structural adhesive. Foaming can be performed while oven-curing the CDP layer.
A disadvantage of such reinforcing elements is that the mechanical properties of the structural adhesive are impaired by the foaming process.